Induced hypothermia is underused after resuscitation from cardiac arrest: a current practice survey

Resuscitation 64 (2005) 181–186

Induced hypothermia is underused after resuscitation from cardiac arrest: a current practice survey夽 Benjamin S. Abella∗ , James W. Rhee, Kuang-Ning Huang, Terry L. Vanden Hoek, Lance B. Becker Emergency Resuscitation Center, Section of Emergency Medicine, University of Chicago Hospitals, 5841 S. Maryland Avenue, MC 5068 Chicago, IL 60637, USA Received 6 July 2004; received in revised form 6 September 2004; accepted 6 September 2004

Abstract Background: Important recent work has demonstrated that the use of induced hypothermia can improve survival and neurologic recovery after cardiac arrest. We wished to ascertain the extent to which physicians were using this treatment, and what opinions are held by clinicians regarding its use. Methods: An internet-based survey of physicians was conducted, with physicians chosen at random from published directories of the Society for Academic Emergency Medicine, the American Thoracic Society, and the American Heart Association. Physicians were questioned regarding use of therapeutic hypothermia, methods employed, and/or reasons why they had not incorporated hypothermia into their care of cardiac arrest patients. Results: Completed surveys were collected from 265 physicians, including those practicing emergency medicine (41%), critical care (13%), and cardiology (24%). Respondents were geographically well distributed and the majority (94%) were at post-training level. Most respondents (78%) practiced at either larger referral hospitals or academic medical centers. When asked if they had ever used hypothermia following cardiac arrest, 87% said they had not. Among reasons cited for non-use, 49% felt that there were not enough data, 32% mentioned lack of incorporation of hypothermia into advanced cardiovascular life support (ACLS) protocols, and 28% felt that cooling methods were technically too difficult or too slow. Conclusion: Despite compelling data supporting its use, hypothermia has yet to be broadly incorporated into physician practice. This highlights the need for improved awareness and education regarding this treatment option, as well as the need to consider hypothermia protocols for inclusion in future iterations of ACLS. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Cardiac arrest; Heart arrest; Hypothermia; Resuscitation; Guidelines

1. Introduction Cardiac arrest carries a greater than 90% mortality rate, leading to over 300,000 deaths in the United States each year [1,2]. Despite the development of pharmacologic therapies for cardiac arrest [3–5] and the improved access to electrical defibrillation [6,7], this mortality rate has not declined 夽 A Spanish and Portuguese translated version of the Abstract and

Keywords of this article appears at 10.1016/j.resuscitation.2004.09.014. ∗ Corresponding author. Tel.: +1 773 834 0730; fax: +1 773 702 3135. E-mail address: [email protected] (B.S. Abella). 0300-9572/$ – see front matter © 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2004.09.014

significantly over the past few decades. Many initially resuscitated patients succumb during subsequent hospitalization [8]. Among the few survivors to hospital discharge, neurologic impairment often remains a lasting morbidity [9,10]. A number of landmark studies, published over the past 4 years, have demonstrated that cooling patients can provide significant survival benefit after initial resuscitation from cardiac arrest [11–14]. Several of these investigations were well-designed randomized controlled trials, providing better evidence for the use of cooling over many pharmacologic interventions after cardiac arrest [15]. For example, one European group demonstrated an improvement in survival to

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hospital discharge with favorable neurologic status in cooled patients compared to normothermic patients surviving arrest (53% versus 35%, respectively), with no significant adverse events from cooling [11]. On the strength of these studies, the International Liaison Committee On Resuscitation (ILCOR) published recommendations supporting the use of induced hypothermia after resuscitation from cardiac arrest due to ventricular fibrillation, and possibly other rhythms as well [16]. Even a small impact on survival and favorable neurologic outcome would lead to important gains for thousands of patients [11]. Despite these developments, it remains unclear whether physicians have begun to use this treatment. Additionally, given that cooling methodology remains cumbersome and poorly studied, compilation of physicians’ initial experiences with hypothermia would help guide future investigations and development of critical pathways, which serve as important instruments to standardize and improve care [17,18]. To evaluate physician experience and opinion regarding induced hypothermia after cardiac arrest, we undertook a survey of U.S. physicians in emergency medicine, critical care, and cardiology, in an attempt to target providers likely to care for cardiac arrest patients. We questioned physicians regarding their current use of hypothermia after cardiac arrest, and their awareness and/or opinions of hypothermia therapy.

2. Methods The study protocol was approved by the University of Chicago Hospitals Institutional Review Board. The study was deemed compliant with the Health Insurance Portability and Accountability Act of 1996 (HIPAA) regulations, given that no specific patient data were collected. 2.1. Study design and selection of participants An internet-based survey was conducted during November 2003. A survey instrument was drafted by three of the authors and piloted among 50 residents and faculty at the University of Chicago Hospitals, to improve clarity and gauge the nature of responses. After this development process, 2000 electronic mail addresses were chosen at random from directories of three professional associations: the Society of Academic Emergency Medicine, American Thoracic Society, and American Heart Association. Randomization was performed by selecting an equal number of names from each page in the directory without regard to geographic location, years in practice or other physician criteria. Potential respondents were only selected if the chosen recipient had MD or DO degrees listed in the respective directory. An invitation to participate in the survey was sent to each address, with a hyperlink leading to the survey itself. The survey was published via a commercial provider (http://www.infopoll.com, Dartmouth, Canada). By following the hyperlink, respondents were presented with a 12-

question survey asking demographic information (e.g., field of practice, geographic location, level of training) as well as questions pertaining to respondent use of induced hypothermia after cardiac arrest (e.g., methodology, reasons for nonuse). An open-ended response was allowed at the end of the survey. 2.2. Primary data analysis Results for each question were compiled using custom software provided by the survey host site. Further analysis and tabulation was performed using a spreadsheet application (Excel, Microsoft Corp., Redmond, WA). Simple statistical analysis was performed using the chi square test function in Excel to test for significance. In presentation of results, percentage values were rounded to the nearest percentage point.

3. Results 3.1. Survey respondent characteristics Of the initial 2000 electronic mail invitations to participate in the survey, approximately 600 were returned due to incorrect or non-functional addresses. Of the remaining 1400 physicians who therefore received invitations, 265 completed surveys resulting in a 19% response rate. Analysis of the demographic questions revealed that physicians represented the fields of emergency medicine (41%), critical care (13%), cardiology (24%) and other fields (22%). 94% were attending physicians, and 78% practiced at either tertiary academic medical centers or large referral hospitals. Most respondents (77%) treated six or more cardiac arrest patients per year. Other demographic data are also shown in Table 1. Finally, physician respondents were reasonably well distributed geographically, as shown in Fig. 1. 3.2. Survey results When asked “Have you ever utilized hypothermia in a patient after resuscitation?”, 87% of physicians responded that they had not (Fig. 2), with respondents in critical care most

Fig. 1. Regional geographic distribution of survey respondents.

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Table 1 Demographic data of respondents

Fig. 2. Distribution of responses to the question “Have you ever utilized hypothermia in a patient after resuscitation?” Differences are significant between each of the three specialization groups, p < 0.05. Two respondents of the entire cohort (n = 265) chose not to answer this question.

likely to have responded that they had used this method of treatment, compared to respondents in emergency medicine or cardiology (p < 0.05). When offered possible reasons why they had not used this modality (Fig. 3), 49% felt that there was not enough data and 32% had not considered this treatment option. 28% felt that cooling methods themselves presented technical impediments (either too difficult or too slow). Among physicians who had used therapeutic hypothermia, results showed that methods employed were consistent with recent publications on cooling as a treatment modality (Fig. 4). The published treatment techniques, namely cooling blankets or ice/cold liquid packing, were used by 65% of respondents. Additionally, 13% of respondents used ice/cold liquid gastric lavage. A further cohort of physicians (17%) reported use of ‘other methods’; for simplicity, our survey did not allow elaboration on this point. At the end of the survey, an open-ended free response space was given for respondents to comment on any aspect

Level of training Attending Resident Fellow

% 94 3 3

Field of practice Emergency medicine Critical care Cardiology Other

41 13 24 22

Practice location Hospital size More than 1000 beds 751–1000 beds 501–750 beds 251–500 beds up to 250 beds

4 19 17 37 23

Staffing Residents and students present No residents or students present

79 21

Hospital type Tertiary academic hospital Referral hospital Community hospital Other

56 22 19 3

Cardiac arrest patients treated per year: Up to 5 patients per year 6–10 patients per year More than 10 patients per year

24 30 47

Note that the majority of physicians are at the attending level, and practice in larger hospital settings (either referral hospitals or academic medical centers larger than 250 beds). Most care for at least six cardiac arrest patients per year. All values are percent.

of the survey or the use of hypothermia. While responses varied considerably among the 80 physicians who chose to give open-ended replies, some themes emerged, such as the desire to learn more about the technique or the need to

Fig. 3. Responses to the question, “Which of the following issues have prevented you from using hypothermia as a therapeutic tool?”. Note that respondents were allowed to choose multiple answers, thus the total percentages add up to greater than 100%.

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Fig. 4. Reponses to the question, “If you do cool patients after cardiac resuscitation, how do you induce hypothermia in your patients?”.

Table 2 Categorization of open-ended responses included in the survey

4. Discussion

Free response theme

Number of respondents

4.1. Poor utilization of therapeutic hypothermia

Plan on using it in future/now developing protocol Lack of training/too many resources required Literature not yet convincing Have not heard of this treatment option Resistance from hospital or other physicians I am interested in technique, want to learn more Other miscellaneous free responses

7 5 4 3 3 3 55

Total number of free response replies

80

Our survey of physician practice has revealed that many physicians have not yet incorporated the use of therapeutic hypothermia after cardiac arrest, despite both strong data and published guidelines recommending its use. This conclusion appears to be consistent across the three major specialties we queried: emergency medicine, critical care and cardiology. Moreover, physicians at academic institutions and tertiary or referral hospitals were over-represented among the survey respondents, making it likely that the degree of hypothermia use reflected in our survey is an optimistic perspective. There are a number of possible reasons why hypothermia has not been readily incorporated into cardiac arrest treatment. Our survey shows that a large number of physicians responded that they did not use hypothermia because they were not aware of the method or because they felt that data were insufficient. A second major possibility suggested by our survey is that whether or not strong literature exists for a cardiac arrest treatment, codification of knowledge in advanced cardiovascular life support (ACLS) guidelines [19] is crucial for broader acceptance and use. Finally, current technical issues may impede the spread of hypothermia use, as cooling blankets and ice packing, the two most readily available and proven methods, are cumbersome and slow to work. However, newer cooling techniques are under rapid development (see below) and therefore these objections may soon become obsolete.

Of the total number of respondents, 80 chose to add comments regarding the use of hypothermia after cardiac arrest. Broad characterization of their responses revealed these themes, which were listed if at least three replies addressed the same point.

overcome resistance from staff and other physicians in the use of hypothermia (Table 2). 3.3. Limitations There are several limitations inherent in a survey study such as this. First, a survey study reflects practice at one point in time. The incorporation of hypothermia induction is certainly in flux, and may change over the next 12 months. Second, we intended only to perform an initial glimpse into opinions regarding the use of hypothermia. Given our low response rate, our sample does not completely reflect the opinions and practice patterns of the whole population of physicians caring for cardiac arrest patients. Specifically, we note that the respondent population was skewed towards physicians practicing in larger hospitals and teaching institutions. This fact, coupled with the probable bias that physicians would be more likely to respond to the survey if they had an interest in cardiac arrest or hypothermia, provides a useful aspect of our study: our results reflect a likely ‘best case’ view of hypothermia use.

4.2. The importance of therapeutic hypothermia Despite the technical difficulties inherent in hypothermia induction, data has accumulated over the past few years to support its use. A number of laboratory studies have demonstrated that cooling after resuscitation from cardiac arrest

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improves both survival as well as subsequent neurologic and cardiac function. These findings have been reproduced using a variety of cooling techniques in different species, including rats [20], dogs [21,22] and pigs [23]. What is especially notable about this body of work is that many of the animal studies show that clinical benefits persist days or weeks after resuscitation, suggesting that the benefit of hypothermia is robust and long lasting. Animal work also supports the notion that cooling should be performed as early as possible to accrue the greatest benefit [21,24]. The induction of hypothermia after human cardiac arrest is not a new idea [25,26], but the technique has found important support from well-performed clinical studies over the past few years [11–14]. In these studies, induction of hypothermia within hours of resuscitation led to impressive gains in survival and neurologic function. Importantly, adverse events, which theoretically might have been promoted by hypothermia, such as infection or coagulopathy, were not found to be significantly increased by cooling. The consensus from these clinical trials suggest that cooling should be initiated promptly after resuscitation from cardiac arrest, and this premise served as a basis for the ILCOR recommendations [16] for hypothermia induction after ventricular fibrillation cardiac arrest. 4.3. Improving utilization of therapeutic hypothermia Our survey results suggest that the following actions are required to improve incorporation of therapeutic hypothermia into practice: 1. Efforts must be given towards physician education via position statements by the various clinical professional societies. 2. The ACLS guidelines, published by the American Heart Association, should be updated to include consideration of therapeutic hypothermia as a post-resuscitation treatment. 3. The community of physicians caring for cardiac arrest patients should be encouraged to share experiences and protocol development with each other at national and international meetings [27], or via the implementation of hypothermia patient data registries. 4. Further investigation of physician practice patterns should be undertaken. Given that the key clinical studies of hypothermia have been conducted in Europe and Australia, it would be interesting to undertake a comparative survey study among physicians in these countries with our present one. We are currently developing such a survey. Over the next few years, it is probable that the technology to induce hypothermia will improve greatly. Methods to cool more expeditiously, such as the development of novel coolant fluids [28], cooling catheters [29] and use of cold IV fluids [30] will make therapeutic hypothermia more accessible to physicians and more practical for heath care staff. More rapid cooling with these newer methods may improve survival even further, as animal data support the notion that earlier cool-

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ing provides the greatest benefit after resuscitation [21,24]. Finally, it remains an open question by what mechanism hypothermia improves outcomes after cardiac arrest. Research involving animal modeling of cardiac arrest will hopefully address this question over the next few years. 5. Conclusions In summary, we have shown that physician use of hypothermia induction in patients resuscitated from cardiac arrest is low. Reasons why physicians have not used hypothermia include lack of awareness of supporting data, technical constraints, and the lack of hypothermia protocol incorporation into ACLS. Better understanding of the pathophysiology of resuscitation [31] and the injury processes on which hypothermia acts will serve to further promote the use of this promising method to save lives. 6. Conflict of interest statement LB Becker has received research funding from Laerdal Medical Corporation to develop new technologies to induce therapeutic hypothermia. All other authors disclose no conflicts of interests. Acknowledgements We wish to thank Dana Edelson, MD and Raina Merchant, MD for critical manuscript review. We also thank Lynne Harnish and Lee Ann Reed for administrative assistance. References [1] Eisenberg MS, Mengert TJ. Cardiac resuscitation. N Engl J Med 2001;344:1304–13. [2] Becker LB. The epidemiology of sudden death. In: Paradis NA, Halperin HR, Nowak RM, editors. Cardiac arrest: the science and practice of resuscitation medicine. Baltimore: Williams & Wilkins; 1996. p. 28–47. [3] Kudenchuk PJ, Cobb LA, Copass MK, et al. Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation. N Engl J Med 1999;341:871–8. [4] Wenzel V, Krismer AC, Arntz HR, et al., European Resuscitation Council Vasopressor during Cardiopulmonary Resuscitation Study Group. A comparison of vasopressin and epinephrine for out-of-hospital cardiopulmonary resuscitation. N Engl J Med 2004;350:105–13. [5] Nolan JP, De Latorre FJ, Steen PA, et al. Advanced life support drugs: do they really work? Curr Opin Crit Care 2002;8:212– 8. [6] Myerburg RJ, Velez M, Fenster J, et al. Community-based responses to impending or actual cardiac arrest and advances in post-cardiac arrest care. J Interv Card Electrophysiol 2003;9:189–202. [7] Caffrey SL, Willoughby PJ, Pepe PE, et al. Public use of automated external defibrillators. N Engl J Med 2002;347:1242–7. [8] Peberdy MA, Kaye W, Ornato JP, et al. Cardiopulmonary resuscitation of adults in the hospital: a report of 14720 cardiac arrests from

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